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Questions and Answers
What is the primary role of acetyl-CoA produced from beta-oxidation?
What is the primary role of acetyl-CoA produced from beta-oxidation?
Insulin stimulates beta-oxidation.
Insulin stimulates beta-oxidation.
False
Name one consequence of enzyme defects in beta-oxidation.
Name one consequence of enzyme defects in beta-oxidation.
Hypoglycemia
Beta-oxidation is crucial for the production of ________ bodies during glucose scarcity.
Beta-oxidation is crucial for the production of ________ bodies during glucose scarcity.
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Match the following products of beta-oxidation with their functions:
Match the following products of beta-oxidation with their functions:
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Which molecule is produced as a result of beta-oxidation?
Which molecule is produced as a result of beta-oxidation?
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The activation of fatty acids occurs within the mitochondria.
The activation of fatty acids occurs within the mitochondria.
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What role does FADH2 play in beta-oxidation?
What role does FADH2 play in beta-oxidation?
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The __________ shuttle system is responsible for transporting fatty acyl groups across the inner mitochondrial membrane.
The __________ shuttle system is responsible for transporting fatty acyl groups across the inner mitochondrial membrane.
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Match the step of beta-oxidation with its description:
Match the step of beta-oxidation with its description:
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During which step of beta-oxidation is NADH produced?
During which step of beta-oxidation is NADH produced?
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Beta-oxidation takes place in the cytoplasm of cells.
Beta-oxidation takes place in the cytoplasm of cells.
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What is the main function of acetyl-CoA produced from beta-oxidation?
What is the main function of acetyl-CoA produced from beta-oxidation?
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Study Notes
Overview of Beta-Oxidation
- Beta-oxidation is a metabolic pathway that breaks down fatty acids into acetyl-CoA molecules.
- This process takes place in the mitochondria of cells.
- The acetyl-CoA molecules can then enter the citric acid cycle for further energy production.
- Beta-oxidation is crucial for energy production, especially during periods of fasting or prolonged exercise.
- It's a four-step cycle that repeatedly cleaves fatty acyl-CoA chains.
Steps of Beta-Oxidation
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Step 1: Oxidation: Acyl-CoA dehydrogenase catalyzes the removal of two hydrogen atoms from the alpha and beta carbons of the fatty acyl-CoA molecule. This produces a trans-Δ2 enoyl-CoA. This reaction also generates FADH2 that enters the electron transport chain.
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Step 2: Hydration: Enoyl-CoA hydratase catalyzes the addition of water across the double bond, creating a β-hydroxyacyl-CoA.
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Step 3: Oxidation: β-hydroxyacyl-CoA dehydrogenase removes two hydrogen atoms from the β-hydroxyacyl CoA converting it to a β-ketoacyl-CoA. NAD+ is reduced to NADH in this step. NADH yields energy in the electron transport chain.
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Step 4: Cleavage: β-ketoacyl-CoA thiolase catalyzes the cleavage of the fatty acyl-CoA molecule into a shortened acyl-CoA molecule and acetyl-CoA. The acetyl-CoA is a substrate for the citric acid cycle. This shortened acyl-CoA molecule now enters the beta-oxidation cycle again, repeating the steps above.
Fatty Acid Activation
- Before beta-oxidation can begin, fatty acids must be activated.
- This involves the attachment of coenzyme A (CoA) to the fatty acid.
- This activation step occurs outside the mitochondrial membrane and requires energy in the form of ATP. The acyl-CoA is then transported across the inner mitochondrial membrane.
Transport Across the Mitochondrial Membrane
- Fatty acyl-CoA molecules cannot directly pass through the inner mitochondrial membrane but need a carrier system.
- This carnitine shuttle system transports the fatty acyl group to the matrix where the beta-oxidation takes place.
- The process involves the transfer of the fatty acyl group to carnitine, which then carries it across the membrane.
- Inside the mitochondrial matrix, the acyl group is transferred back to CoA.
Importance of Beta-Oxidation
- Provides a significant source of energy, particularly during prolonged exercise or fasting.
- Critical for maintaining blood glucose levels, preventing hypoglycemia.
- Plays a role in the synthesis of some cellular components.
- Crucial for the production of ketone bodies—alternative fuels when glucose is scarce.
Regulation of Beta-Oxidation
- The rate of beta-oxidation is regulated to maintain energy balance in the body.
- Various hormones, like glucagon and epinephrine, stimulate it, while insulin generally inhibits it.
- The activity of enzymes involved in beta-oxidation is also regulated by allosteric effectors.
Products of Beta-Oxidation
- Acetyl-CoA: Enters the citric acid cycle.
- NADH and FADH2: Donate high-energy electrons to the electron transport chain in order to synthesize ATP.
- ATP (indirectly): ATP is generated through the electron transport chain and oxidative phosphorylation which are powered by the reducing equivalents (NADH/FADH2) created during this process.
- Ketone bodies: Can be produced when there is excess acetyl-CoA and insufficient oxaloacetate (low carbohydrate diet).
Conditions Associated with Dysfunction in Beta-Oxidation
- Defects in enzymes involved in beta-oxidation can lead to various clinical conditions, including metabolic disorders.
- These disorders can manifest during infancy, childhood, or adulthood, presenting with symptoms such as hypoglycemia, muscle weakness, and even life-threatening consequences.
Dietary Implications (Brief)
- High-fat diets affect beta-oxidation.
- Dietary fats are important to supply essential nutrients and energy, but excessive fat consumption might have implications on metabolic health in some individuals.
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Description
This quiz explores the metabolic pathway of beta-oxidation, which breaks down fatty acids into acetyl-CoA. You'll learn about the significance of this process in energy production, especially during fasting and exercise, as well as the detailed steps involved in this cycle. Test your understanding of the biochemical reactions and their importance in metabolism.